#stage{
    width: 320px;
    height: 568px;
    margin: auto;
    background: red;
    color: white;
    overflow: hidden;   /*隐藏背景图多余部分*/
    position: relative;
}
.bg1{
    background-image: url(../img/bg.png);
    height: 768px;
    width: 100%;
    position: absolute;
    top: -200px;
}
.bg2{
    background-image: url(../img/bg.png);
    height: 768px;
    width: 100%;
    position: absolute;
    top: -968px;
}
.plane{
    height: 126px;
    width: 102px;
    background-image: url(../img/me1.png);
    position: absolute;
    bottom: 0;/*下边距0*/
    z-index: 1;    /*绝对定位才生效由于div写在了背景图后边,所以可写可不写*/
}
.enemy1{
    width: 57px;
    height: 43px;
    background-image: url(../img/enemy01.png);
    position: absolute;
    left: 30px;
}
.enemy2{
    width: 69px;
    height: 99px;
    background-image: url(../img/enemy02.png);
    position: absolute;
    left: 120px;
}
.enemy3{
    width: 169px;
    height: 258px;
    background-image: url(../img/enemy03.png);
    position: absolute;
    left: 150px;
}
/* 子弹 */
.bullet{
    width: 5px;
    height: 11px;
    position: absolute;
    background-image: url(../img/bullet01.png);
    z-index: 2;
}